This invention relates generally to the packaging of electronic devices and, in particular, to a circuit board spacer for maintaining two relatively flexible circuit boards in a circuit board rack in physical isolation from one another.
In the art of packaging and interconnecting electronic devices, there is a notable trend towards high density packaging. In the digital computer technology, for example, it has been found desirable to package electronic devices as closely together as possible in order to increase the operational efficiency of the overall data processing system.
A common packaging arrangement throughout the electronics industry is the placement of electronic devices on printed circuit boards. Often a plurality of circuit boards are stacked one above the other in a circuit board rack to achieve higher packaging density. The spacing between adjacent circuit boards is a critical factor, since on the one hand it is highly desirable to position adjacent boards as closely as possible to achieve the benefit of high density packaging and on the other hand adjacent boards must not be permitted to come into physical contact with one another. Physical contact between adjacent boards or the components or lead projections thereof can result in damage to the boards or their components when circuit boards are inserted or removed from the circuit board rack. Also, physical contact between the boards or their components ordinarily results in electrical contact as well, which violates the electrical integrity of the circuitry on the boards and results in decreased electrical performance, burned circuit boards, or blown out circuit breakers.
The use of large, highly populated, relatively flexible circuit boards, as is common in the digital computer industry, substantially increases the changes of adjacent boards making physical contact with one another, since after a period of time circuit boards which are suspended by their edges have a marked tendency to sag in the middle, thereby coming into contact with another board. The high density packaging of these boards, in the form of a great many electronic devices per board, increases the probability of board sag. The tendency of operational electronic equipment to vibrate also increases the opportunity for board contact.
A variety of circuit board spacers are known in the prior art in the form of spacer pins, sliders, brushes, and rubber rollers; however, they have been found to be unsatisfactory because of their tendency to snag and damage board components or to be subject to excessive wear and rapid deterioration.
A satisfactory circuit board spacer must address itself to several specific problems. First, it should be constructed of an electrically insulating material to prevent shorting between adjacent circuit boards. Secondly, it should permit relatively easy insertion and removal of circuit boards. It should also be relatively long-wearing, and preferably have a life-time equal to or exceeding that of the board itself. Lastly, it should be relatively simple in construction and low in cost. The present invention is directed to a novel circuit board spacer which satisfies these requirements.